Flavoring agents, such as sweeteners and spices, are widely used in food products. In some cases, particularly during cooking and baking, some of the flavoring materials are unstable and are destroyed during the cooking process.
One sweetening material that is particularly sensitive to the combination of heat and an aqueous environment is aspartame, the dipeptide sweetener aspartic acid-phenylalanine methylester. Although aspartame is not unstable at elevated temperatures, the combination of an aqueous environment and high temperatures, such as are encountered during baking (about 150.degree.-300.degree. C.) breaks down the dipeptrde molecule and destroys the sweetening ability of the compound.
One method heretofore used for stabilizing food additives is by microencapsulation. However, in most microencapsulation methods, the active ingredient is protected and stabilized not only during preparation, but also remains encapsulated while the food product is being consumed. The food additive agent is then released either in the stomach or intestines, either through diffusion or when the coating layer is dissolved (i.e., in a pH-dependent or other manner). While this method is acceptable for administration of medications or vitamins which need not be available to the consumer until they reach the stomach or intestines, it is unacceptable for flavoring agents, which are designed to be experienced while the food product is in the mouth.
In the case of flavoring agents for foods, it is crucial that the active flavoring ingredient be available to the taste receptors in the mouth and nose at the very beginning of tasting and eating the food product.
Microencapsulation has been used heretofore for protecting flavoring ingredients in foods, although without complete success.
Graves, in U.S. Pat. No. 3,914,439, discloses a dry particulate flavor composition comprising liquid flavoring oils which are absorbed onto sugar crystals which are coated with hydrogenated vegetable oil. The crystals are then sealed with a shellac coating to form a dry, free-flowing particulate flavor compositions. These flavor compositions are used in tea brewing bags, where contact with hot water melts the vegetable oil and releases the flavor.
Eichel, in U.S. Pat. No. 3,317,433, discloses heat rupturable capsules which are used as components in an external embedding substance which will react or combine with the core entity materials when the core materials are released by heat rupture. Examples of this include capsules containing solvents or plasticizers embedded in a solid adhesive film.
Seaborne et al., in U.S. Pat. No. 4,810,534, disclose edible film coating compositions of low moisture permeability comprising crosslinked, refined shellac and an edible member. The coating compositions are useful as a moisture barrier in composite food articles having phases in contact which differ substantially in water activity.
Wurzburg et al., in U.S. Pat. No. 3,091,567, disclose encapsulating agents with controlled water repellency which can contain volatile, relatively water-insoluble flavors or other substances.
Ciliberto et al., in U.S. Pat. No. 4,288,460, disclose a method for protecting granular water-soluble food ingredients which deteriorate upon exposure to the atmosphere by encapsulating these ingredients in a protective coating consisting essentially of a fatty acid derivative selected from the group consisting of polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate and lecithin; propylene glycol; and a flow agent such as fumed silica or carboxymethylcellulose. The coated particles have a long shelf life but are substantially instantaneously soluble in water.
Kirn et al., in U.S. Pat. No. 4,710,391, disclose a flavoring agent used to flavor fried foods which is encapsulated so that the flavoring agent can be readily removed from the oil used to fry the food products. A high melting point fat coating on the flavoring agent helps to protect the encapsulant from water and from physical damage prior to and during frying.
Tsau et al, in U.S. Pat. No. 4,704,288, disclose a heat stabilized compositions of aspartame and a partially hydrogenated vegetable oil melting at about 120.degree. F. or above. The particles are formed into 8-40 standard mesh particle size, i.e., from 420 to 2308 microns. Both the type of fat and the particle size are critical to this process.